Background Angiogenesis and lymphangiogenesis are critical for several allergic, inflammatory, and neoplastic disorders. Mast cells infiltrate the sites of inflammation and tumors. Objective We ...sought to characterize the expression and functions of vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) in human mast cells. Methods VEGF expression was evaluated by means of RT-PCR and Western blotting in primary human lung mast cells and in the mast cell lines LAD-2 and HMC-1. Angiogenic activity of mast cell supernatants was determined by using the chick embryo chorioallantoic membrane assay. VEGFR expression was assessed by means of RT-PCR and flow cytometry. Modified Boyden chambers were used for chemotaxis assay. Results Human mast cells express VEGF-A, VEGF-B, VEGF-C, and VEGF-D at both the mRNA and protein level. Prostaglandin E2 (PGE2 ) enhanced the expression of VEGFA , VEGFB , and VEGFC , whereas an adenosine analog (5′-N-ethylcarboxamido adenosine NECA) increased VEGFA , VEGFC , and VEGFD expression. In addition, PGE2 and NECA enhanced VEGF-A release, and supernatants of PGE2 - and NECA-activated human lung mast cells induced angiogenic responses in the chorioallantoic membrane assay that were inhibited by an anti-VEGF-A antibody. Mast cells expressed mRNA for VEGFR1 and VEGFR2 . These receptors were present on the mast cell surface. VEGF-A165 , VEGF-B167 , VEGF-C, VEGF-D, and placental growth factor 1 induced mast cell chemotaxis. These chemotactic effects were mediated by the activation of both VEGFR-1 and VEGFR-2. Conclusion Our data indicate that human mast cells are both a source and a target of angiogenic and lymphangiogenic factors and therefore might play a role in inflammatory and neoplastic angiogenesis through the expression of several forms of VEGFs and their receptors.
Background Secreted phospholipases A2 (sPLA2 s) are released in plasma and other biologic fluids of patients with inflammatory, autoimmune, and allergic diseases. Objective We sought to evaluate ...sPLA2 activity in the bronchoalveolar lavage fluid (BALF) of asthmatic patients and to examine the expression and release of sPLA2 s from primary human lung mast cells (HLMCs). Methods sPLA2 activity was measured in BALF and supernatants of either unstimulated or anti-IgE–activated HLMCs as hydrolysis of oleic acid from radiolabeled Escherichia coli membranes. Expression of sPLA2 s was examined by using RT-PCR. The release of cysteinyl leukotriene (LT) C4 was measured by means of enzyme immunoassay. Results Phospholipase A2 (PLA2 ) activity was higher in the BALF of asthmatic patients than in the control group. BALF PLA2 activity was blocked by the sPLA2 inhibitors dithiothreitol and Me-Indoxam but not by the cytosolic PLA2 inhibitor AZ-1. HLMCs spontaneously released a PLA2 activity that was increased on stimulation with anti-IgE. This PLA2 activity was blocked by dithiothreitol and Me-Indoxam but not by AZ-1. HLMCs constitutively express mRNA for group IB, IIA, IID, IIE, IIF, III, V, X, XIIA, and XIIB sPLA2 s. Anti-IgE did not modify the expression of sPLA2 s. The cell-impermeable inhibitor Me-Indoxam significantly reduced (up to 40%) the production of LTC4 from anti-IgE–stimulated HLMCs. Conclusions sPLA2 activity is increased in the airways of asthmatic patients. HLMCs express multiple sPLA2 s and release 1 or more of them when activated by anti-IgE. The sPLA2 s released by mast cells contribute to LTC4 production by acting in an autocrine fashion. Mast cells can be a source of sPLA2 s in the airways of asthmatic patients.
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